I did spend the day checking out transomrepair.com. The pourable transom. I think that would do the trick. couple of points with that though.
1. ALL wood needs to be removed. That is a daunting task. port and starboard ends of the transom are tough to get at. The top of the transom sits under the aft gunnel.
2. Need to keep both sides of the fiberglass. I've read ideas of chainsawing, drilling etc. but this it tough when you can't poke a hole in either side. But I think a good solid day's work would probably clean that transom out of all the wood. I guess you right down below the bilge drain to the hull bottom. I picture pouring this stuff in and it running out into the bilge! That would suck.
3. This stuff will not bond to any wood whatsoever.

Anyone try this stuff?

Mike